With the rapid development of display technology, touch screen panels have become popular in people's life. At present, according to the principle of operation, touch screen panels can be classified into: resistive type, capacitive type, infrared type, surface acoustic wave type, electromagnetic type, vibrating wave inductive type, suppressed total internal reflection optical inductive type, and so on. The composition structure of a touch screen panel can be classified into: touch sensor add-on type (double layer), touch sensor on cover surface (single layer), touch sensor on panel, and touch sensor in panel (embedded type). Among them, the structure of touch sensor in a panel can both reduce the overall thickness of the touch screen panel and greatly reduce manufacturing costs of the touch screen panel, hence wining good graces of panel manufacturers.
At present, the design of touch sensor in a panel is mainly realized in the resistive type, the capacitive type, the optical type or the like sensing mode. Among them, resistive sensing technology belongs to the low end sensing technologies resulting in products with a short life. Capacitive sensing technology is mainly suitable for medium and small sizes, namely the touch screen panels of 10 inches or below. While optical sensing technology is not limited in size, obtains products which have a long life and are relatively stable. However, optical type touch screen panels depend on light environment and can not realize touch operation without light.